SMUAtypicalTeratogens (1)

Prenatal Risk and Teratogens

Period of the Zygote

• Timeline of Zygote Development:

  • 1. Ovulation: Egg cell from ovary enters fallopian tube (9-16 days of the menstrual cycle).

  • 2. Fertilization: Occurs in the upper third of the tube, within 24 hours after ovulation.

  • 3. First Division: Egg cell divides (2 cells at 36 hours, 4 cells at 48 hours).

  • 4. Blastocyst Formation: 4 days post-fertilization—a hollow ball of about 100 cells.

  • 5. Implantation Timeline:

    • Day 4-5: Zygote enters the uterus.

    • Day 6-7: Begins to attach to the uterine wall.

    • Day 12-14: Zygote fully implanted in the uterus.

Cell Duplication and Development

• Process Overview:

  • Fertilization leads to zygote formation, which undergoes cell duplication.

  • Embryonic Disk Development: Forms as zygote develops within the uterine environment.

  • Key Structures Established:

    • Uterus, cervix, amniotic fluid production, and placental development.

The Embryonic/Fetal Environment

• Structures Explained:

  • Placenta: Facilitates nutrient exchange between mother and fetus.

  • Umbilical Cord: Contains blood vessels, connecting the fetus to the placenta.

  • Amniotic Sac: Houses the developing fetus and allows movement.

Teratogens

• Definition:

  • Agents that cause abnormal fetal development, including diseases, drugs, and environmental hazards (e.g., pollution).

• Impact:

  • Teratogens may affect the fetus without harming the mother (example: Accutane).

General Risk Factors for Prenatal Development

• Key Factors:

  • Maternal Age: Risk associated with being too young (<20) or too old.

  • Nutritional Status: Importance of protein, vitamins, and minerals (e.g., folic acid).

  • Maternal Stress: Can lower oxygen to the fetus and lead to unhealthy behaviors.

• Poverty-Related Risks:

  • Limited access to prenatal care, nutrition, and education about development increases risk.

Specific Risk Correlates

• Low Birthweight Association:

  • Correlated with adult diseases (e.g., heart disease).

  • Historical evidence from Dutch women's experiences during WW2.

Vulnerability to Teratogens

• Critical Periods of Development:

  • Different organs develop during specific times, with the CNS having a prolonged development phase.

• Timing of Exposure:

  • Most critical exposure occurs during the embryonic stage (weeks 2-8).

Physiological Impacts of Teratogens

• Specificity of Effects:

  • Individual teratogens will impact specific body systems; for instance, maternal rubella affects hearing and vision.

• Dose-Response Relationship:

  • Longer exposure or higher doses typically lead to greater damage.

Genetic Factors and Susceptibility

• Genotype Influence:

  • Some fetuses are more susceptible based on genetic factors of both the mother and fetus.

Late Onset Damage From Teratogens

• Timing of Manifestation:

  • Damage may be apparent at birth or emerge later in life (e.g., withdrawal symptoms in newborns).

  • Examples of long-term outcome—DES use leading to increased cancer rates in women.

Psychological and Physical Damage

• Fetal Alcohol Syndrome (FAS):

  • Destructive impact includes developmental issues and physical abnormalities (e.g., microcephaly, heart defects).

• Maternal Care Implications:

  • Caregiver addiction can lead to inconsistent care, raising infant stress levels.

Summary

• Teratogens:

  • Affect fetal development during critical periods unique to different organs.

  • Most vulnerability lies within the embryonic stage, resulting in specific deviations such as FAS.